A bit back I opened my office mini fridge and found that it was warm. I checked all the obvious things: it was plugged in and getting power, and the thermostat was set correctly. Deeper diagnostics revealed that the thermostat was faulty. No matter the thermostat setting, it was not engaging to cool the fridge. If I bypassed the thermostat and manually (i.e. shorted the compressor leads) started the compressor the fridge cooled as it should.
I was unable to find an OEM replacement thermostat but figured I could make a replacement for less than a new fridge would cost.